Displacement does not work with GeomSubsets

**Describe the bug**
If you use kick or, in Houdini, Direct USD Render, displacement applied to a GeomSubset does not work. There is no displacement in the rendered image. In the Arnold log, you get an Ill-formed SdfPath error that looks like this:

`Warning: in SdfPath at line 151 of S:\gocd\pipelines\kook\kook\usd\build\usd-22.11_windows-x86_64_static_vc-14.3_cxx14\pxr\usd\sdf\path.cpp -- Ill-formed SdfPath : syntax error`

or

`Warning: in SdfPath at line 151 of S:\gocd\pipelines\kook\kook\usd\build\usd-22.11_windows-x86_64_static_vc-14.3_cxx14\pxr\usd\sdf\path.cpp -- Ill-formed SdfPath : syntax error
`


**To Reproduce**
- Here's a usda file with displacement on one half of a sphere:
[Displacement_Test.zip](https://github.com/Autodesk/arnold-usd/files/11296752/Displacement_Test.zip)

**Used Software Versions**
- Arnold 7.2.1
- Houdini

Start by opening Displacement_Test.zip and reproducing the GeomSubset displacement case with kick or Houdini Direct USD Render, then inspect the Arnold log for the ill-formed SdfPath warnings. Done means displacement renders correctly for the supplied sphere without those warnings.

Written by the indexing model from the issue text.